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Fix a loose secondary mirror holder?

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#1 MFMAstro



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Posted 13 April 2009 - 06:29 PM

The secondary mirror holder in the corrector plate of my 8" Schmidt-Newtonian has come loose and now rotates in the corrector plate when I try to adjust the collimation screws. Anyone know how to fix this?



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Posted 26 April 2009 - 08:26 AM

This happens , or will happen, to all SN owners sooner or later. What I did on my SN10 is the following:

1. Cut a hole in a piece of heavy paper [like business card paper or heavier] so the paper will fit over the locking ring on the secondary holder. This is to protect the corrector for step two and three.

2. Snug the corrector lock ring by hand then rotate the secondary using the three collimation screws for leverage until the primary is centered in the focus tube. A pinhole cap in the eyepiece holder works well for this. This is not the most precise way but will get you close. There are better techniques for aligning the secondary in some of the LXD forums.

3. Take a channel lock pliers and put tape over the ends to keep from marring the corrector lock ring and gently grip and snug the secondary locking ring. DO NOT OVER TIGNTEN. Recheck that the secondary alignment did not change. You may have to hold onto the three alignment screws while tightening.

This should get you back in the game.


#3 MFMAstro



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Posted 06 May 2009 - 04:06 PM

The problem has been fixed. Thanks.


#4 samtarani



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Posted 28 August 2013 - 04:58 PM

I have the same issue with the secondary coming lose! However, after adjusting and collimation, I noticed that the secondary remained lose and keeps getting off as I move the scope around. I tried in tightening the tension ring to tighten the mirror but I could not move it in any direction regardless of how much force I applied without dangering the corrector plate. It seems to be stuck. Cant loosen or tighten it at all! Am I doing something wrong here? Is there anyone who had similar situation?

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